Ginny L. Adams

Critical Swimming Speed and Behavior of Juvenile Shovelnose Sturgeon and Pallid Sturgeon

Abstract The swimming performance of hatchery-reared, juvenile shovelnose sturgeon Scaphirhynchus platorynchus and pallid sturgeon S. albus was studied in a laboratory swim tunnel at 20°C and 10°C. The mean 30-min critical swimming speed was not significantly different between species at either temperature (36.9 cm/s for shovelnose sturgeon and 35.9 cm/s for pallid sturgeon at 20°C, 19.4 cm/s for shovelnose sturgeon and 15.0 cm/s for pallid sturgeon at 10°C). Free swimming (swimming without contact with the substrate) was observed less than 18% of the time at speeds greater than 15 cm/s. As speed increased, pallid sturgeon swam significantly less in the water column at 20°C; however, speed had no effect on percent free swimming among shovelnose sturgeon at 20°C. The results of this study indicate that, over the temperature and size range tested, shovelnose sturgeon and pallid sturgeon probably do not segregate in rivers due to different swimming or station-holding abilities

Oral Grasping: A Distinctive Behavior of Cyprinids for Maintaining Station in Flowing Water

Abstract We examined oral grasping behavior, a unique and relatively unknown method of maintaining station against flow, in nine species of North American cyprinids to determine whether oral grasping was used by a range of cyprinid species and to further investigate the relationship between oral grasping and water velocity. Fish were subjected to a stepwise increasing velocity test in a 100-liter laboratory swim tunnel that had wire mesh (0.6-mm diameter) attached to a flow filter serving as the grasping substrate. Frequency and duration of oral grasping events were noted for a particular fish during each velocity increment. We observed 608 grasping events, and oral grasping behavior was exhibited by all nine species examined. Mean number of grasping events was high (28.4/trial) for Cyprinella venusta, intermediate (approximately 18/trial) for Cyprinella camura, and Notropis longirostris, and low (< 5/trial) for Notropis texanus, Notropis maculatus, and Notropis wickliffi. Although critical swimming speed varied among species, the water velocity at which oral grasping behavior initially appeared (threshold grasping velocity), expressed as a percentage of critical swimming speed, was approximately 70–80% for most species tested. Oral grasping may be triggered by the onset of muscular fatigue, and is an attempt by minnows to maintain position in water velocities exceeding aerobic swimming ability. We speculate that minnows in lotic environments use oral grasping when high, energetically demanding water velocities are unavoidable, such as during a flood.

Survival and precopulatory guarding behavior of Hyalella azteca (Amphipoda) exposed to nitrate in the presence of atrazine

Nitrate is one of the most commonly detected contaminants found in aquatic systems with other pesticides such as atrazine. The current study examined potential combined effects of nitrate and atrazine on adults of the freshwater amphipod Hyalella azteca, using survival and precopulatory guarding behavior as toxic endpoints. Although significant differences in acute toxicity with nitrate alone and in binary combination with atrazine (200 µg/L) in water-only tests were not consistently observed for each time point, potential biologically relevant trends in the data were observed. Posttest growth and behavioral observations (10-day period) conducted after 96-hour exposure suggested that atrazine and nitrate at these concentrations did not result in delayed effects on H. azteca. However, when test conditions were modified from standard toxicity tests by feeding amphipods, nitrate was found to be more toxic, with a reduction in median lethal concentration (LC50) values of approximately 80%. We also demonstrated that nitrate exhibits a dose-response effect on precopulatory guarding behavior of H. azteca, suggesting that reproductive effects may occur at environmentally relevant concentrations.

Cottus specus, a new troglomorphic species of sculpin (Cottidae) from southeastern Missouri

Cottus specus, a new species, is described from the karst regions of the Bois Brule drainage in eastern Missouri, USA. Cottus specus is distinguishable from all members of the genus Cottus using both genetic and morphological characters, including eye size and cephalic pore size. Cottus specus represents the first description of a cave species within Cottus. The addition of C. specus brings the total number of recognized species of Cottus to 33 in North American fresh waters.

Two Catastrophic Floods: Similarities and Differences in Effects on an Ozark Stream Fish Community

In December 1982 a devastating flood occurred in Piney Creek, in the rural Ozark Mountains in Izard County, Arkansas, with vertical stage rises of 2–4 m in the headwaters, 11–12 m at downstream locations, and an estimated return time of 50–100 years. Physical effects in the watershed were catastrophic, with extreme scour and rearrangement of the stream bed, destruction of riparian forest, and deposition of huge amounts of sand from the creek in adjacent pastures or forest. In spite of the extreme nature of this winter flood, residual effects on the overall fish community of the watershed were minimal, and by eight months after the event, the community was virtually indistinguishable from that in the previous summer. In March–April 2008 flooding of equal or greater magnitude than the 1982 flood again occurred in Piney Creek. We followed effects of the spring 2008 flood on local fishes at five long-term fixed sites in the watershed, and on the fish community pooled across those sites, four months after the 2008 flood, and again in 2010 and 2012. In spite of the severity of the 2008 springtime flood, the community before and after was relatively similar qualitatively and quantitatively. But multivariate analyses of the fish community showed more change after the 2008 flood, and in a directional trajectory, than had occurred after the 1982 flood. At the five individual sites, changes in fishes after the 2008 flood were idiosyncratic, with two sites showing marked changes immediately after the flood, with only one subsequently returning toward its former structure. Fishes at all five sites showed more change in multivariate space after the 2008 than after the 1982 flood. In the summers after both floods some cyprinid and catostomid species showed sharp increases in numbers of young-of-year. Differences in the effects of the two floods on the fish community could relate to their timing, with springtime flooding having more effects on fish than the winter flood. Similarities between the two floods with respect to increased production of young-of-year could relate to the scouring of fines (silt and sand) by the floods, providing clean gravel and cobble with more interstitial spaces that could provide protection for fish eggs or larvae, and more microhabitat for food organisms used by young fishes such as micro- or macroinvertebrates. Regardless of mechanisms, much remains to be learned about the effects of extreme floods on stream fish communities, particularly in light of the potential for increased frequency of extreme events as global climate changes continue.

Ecology of the redfin darter and a potential emerging threat to its habitat

The basic biologies and ecologies of most freshwater fishes throughout the world are poorly understood. But such knowledge may be critical for conservation decisions. The redfin darter (Etheostoma whipplei), a poorly understood fish species, is an excellent model for highlighting this situation. Much of the limited range of this species is experiencing nontraditional natural gas extraction activities including hydraulic fracturing, which may be a significant source of silt input for streams. We investigated aspects of the ecology and metrics of reproductive success of redfin darters in central Arkansas. We examined habitat occupation through quantitative surveys of fish assemblages and habitat variables, and reproductive life history through field and laboratory surveys in Cypress Creek, Arkansas. We also examined the proportion of young fishes in populations relative to intensity of natural gas extraction activity. Ordination analysis found habitat gradients relating primarily to stream size. Redfin darters had the highest relative abundance in samples in small, high gradient streams. Redfin darters reproduce in the spring, peaking with the rainy season, using larger substrate than their close relatives. Reproductive success appears to be negatively related to natural gas extraction intensity. Redfin darters reproduce at both a time and in a habitat which may be especially susceptible to siltation from natural gas extraction activities, which may be reflected in fewer young fishes in populations. Our research highlights the importance of life history data in understanding responses to novel disturbances in freshwater fishes.

Life History and Spawning Behavior of the Western Sand Darter (Ammocrypta clara) in Northeast Arkansas

Abstract Members of Ammocrypta (Percidae), known as sand darters, have experienced widespread population declines, yet little is known regarding their ecology and life history. The purpose of this study was to examine life history traits and provide much needed information on the western sand darter (Ammocrypta clara) from a population in Northeast Arkansas. The Strawberry, Black, and Current rivers were sampled by seine or trawl from Jun. 2007–Sep. 2008. Life history traits were examined on 379 specimens. Mean size was 42.9 mm standard length (max. 50 km SL) and males and females reached maturity between 35–40 mm SL. The spawning season was May to Aug. and mean monthly gonadosomatic index (GSI) ranged from 3.4–4.9%. Gravid females averaged 57 eggs per clutch and mean egg size was 0.79 mm across mature, ripening, and ripe stages. Significant relationships existed between female standard length, ovarian mass, and clutch size. Observation of captive specimens in aquaria revealed crepuscular spawning with eggs (mean  =  1.22 mm) buried singly in the sand and clutches released over short periods of time (hours to days). Overall, A. clara from Arkansas possessed several life history traits that differed from data reported for A. clara in Wisconsin and other species of Ammocrypta. We found that fish were smaller in size, had lower GSI values, smaller clutch sizes, and smaller egg sizes compared to other Ammocrypta, reflecting potentially important life history trade-offs between size and age (longevity) and the relationship among GSI, clutch size, and egg size.

Fish Assemblage of a Cypress Wetland within an Urban Landscape

Abstract Fishes were sampled from Gillam Park Wetland, a small cypress swamp located within the city limits of Little Rock, AR during Fall 2005. The objectives of this research were to contribute to our knowledge of understudied wetland habitats in Arkansas, determine the status of the fish community in an urban wetland, and provide baseline data for future monitoring of this unique site. We collected 20 total species from three wetland sections (lower, middle, upper). Although fish community composition varied among the sections, species richness was similar across wetland sections. Fyke nets were more effective at capturing fish along the heavily vegetated and structured shorelines than either seines or funnel traps. The fish community residing in Gillam Park Wetland indicates that this “urban wetland” is functioning and seemingly healthy despite its proximity to anthropogenic impacts. Furthermore, Gillam Park Wetland is located along a major physiogeographic boundary that may play an important role in the distribution and conservation of several swamp specialist species in Arkansas.

Structure and function of large wood in Ozark headwater streams and its relationship to fish community structure

Fish community structure in headwater streams is often influenced by a suite of abiotic variables, such as water depth and flood frequency, channel substrate composition, and in-stream large wood (LW). Wood retained in streams and rivers performs a variety functions; for example, it alters flow, stores sediments, and provides habitat for aquatic biota. The objectives of this study were to (1) quantify and characterize LW, (2) quantify the geomorphic functions of LW, and (3) identify the relationship between LW and fish community structure in Ozark headwater streams. Ten stream reaches with a gradient of LW were sampled in the Ozark-St. Francis National Forest, AR, USA. Single LW pieces, organic accumulations, and root wads were quantified and the geomorphic function of all LW recorded. Fish were identified, enumerated, and massed. LW density in our 10-study streams ranged from <1 to 12 per 100 m2 and >50% functioned to store sediments, stabilize banks, or retain organic matter. Larger diameter wood was associated with altered flow (r = 0.64, p = 0.04) and LW storing sediments tended to also stabilize banks (r = 0.73, p = 0.02). There was no relationship between LW metrics and total fish abundance or biomass; however, stream reaches with higher volumes of organic accumulations supported higher creek chub (r 2 = 0.75, p = 0.005) and southern redbelly dace biomass (r 2 = 0.62, p < 0.02). Although LW densities were among the lowest recorded for US streams, LW still played an integral role in structuring stream geomorphology and providing habitat to some dominant headwater fish species.